Weak current College】 【ATX power supply works.

<br> <br> Since the launch of the first IBM PC, computer power supply from AT to ATX power supply. Today, the PC power is based on the IBM personal computer standard. The ATX power supply on the market, whether it's brand .power or other brand power, circuit theory point of view, are generally in AT, on the basis of the power supply made appropriate changes in development, so that we get to the ATX power supply, on the circuit principle generally similar. In the process .of localization, computer power supply technology is also determined by domestic manufacturers gradually assimilate, to produce a large number of State-owned brand power. Computer power is not a high-tech products for the domestic manufacturers of technology and manufacturing strength, should be able .to produce power products at great prices. However, throughout the entire computer power market situation is unsatisfactory, many power products exist in various materials and quality issues, the failure rate is high. <br> <br> ATX power supply circuit structure is complex ., the part of the circuit is not only the functional cooperate, and permeability, and various circuit parameters set very strict, slightly inappropriate the circuit doesn't work. Its main circuit schematic diagram shown in Figure 1, you can see from the diagram, .the entire circuit can be divided into two parts: part from the power supply input to switch transformer T1 circuit before (including auxiliary power supply of the original side circuit), the part of the circuit and AC 220V voltage directly connected, touch will be subjected .to electric shocks, known as the high voltage side circuit; the other part to switch transformer T1 circuit, not in the future and is directly connected to the AC 220V, known as the low pressure side of the circuit. Both through C03, C04, .capacitance-voltage porcelain C05 constitute circuit to eliminate static electricity. The principle of the block diagram shown in Figure 2, you can see from figure úcircuit by AC input circuit, Rectifier filter circuit, push-pull switching circuits, auxiliary switching power supply, PWM .pulse width modulation circuit, PS-ON control circuits, protection circuit, output circuit and PW-OK signal circuit. Find out all parts of the circuit works and their relationship to our service malfunction judgment is useful, here's a quick look at the various components .of the work. <br> <br> 1. AC input circuit <br> <br> AC input circuit including input protection circuit and anti-interference circuit, etc. Input protection circuitry includes AC input circuit of over-current, over- .voltage protection and current limiting circuit; a antijamming circuit has two roles: one refers to the computer power on by power network access interference signal suppression capability: refers to the switching power supply's power system harmonics into oscillation on other devices and display of interference and the .interference of the microcomputer itself. Typically requires access to the computer through the network of interference signal suppression ability to compel the other through the network to the computer and other equipment of interference. <br> <br> 2. the rectifier circuit: <br .> <br> Including the rectifier and filtering of two parts, an AC power circuit for rectifier filtering, provide for switch push-pull circuit ripple smaller DC voltage. <br> <br> 3 auxiliary power: auxiliary power itself is a complete switching .power supply. As long as a power-ATX power supply, auxiliary power began to work, the output voltage, two road all the way to + 5VSB power supply, the output is connected to the ATX motherboard power supply monitoring part of "," .as its operating voltage, enabling the operating system can be managed directly to power. With this feature, enable remote boot, complete PC wake-up function; the other one output voltage protection circuit, control circuit, circuit power supply. <br> < .br> 4, push-pull switching circuit: <br> <br> Push-pull switching circuit is an ATX power supply of the main part of the DC voltage transformation into a high frequency AC voltage, and plays a part of the output and .input power network isolation. Push-pull switching valve is the part of the core components of the circuit, the PWM circuit transmission signal for excitation signal, when the PWM circuit for protection circuit fault of their own action or does not work, push-pull .switching valve was radical-level non-driven pulse it does not work, the circuit is closed, this work called it stress work. <br> <br> 5, PWM pulse width modulation circuit: <br> <br> PWM (PulesWidthModulation .) ie PWM circuit, its function is to detect the output DC voltage, comparison with the reference voltage, zoom, control oscillator pulse width, and thereby control push-pull switching circuit to maintain the stability of the output voltage, mainly by ICTL494 and surrounding .components. <br> <br> 6, PS-ON control circuit: <br> <br> ATX power supply's main characteristics is that it does not use traditional power switch to control the power supply is working, instead of using "+ 5VSB ., PS-ON "to realize the power of open and closed, as long as you control the" PS-ON "signal level changes, we will be able to control the power of open and close. Power supply S-ON control circuit accepts .PS-ON signal control, when the "PS-ON" less than when you turn on power supply 1V Volt, greater than 4.5 Volt powering it. Main cabinet surface trigger button switch (non-locking switch) Control Board's "power monitoring part" .output status, but also the available procedures to control "power monitoring pieces" output, such as in the WIN9X platform, to issue the shutdown command, so that the "PS-ON" becomes a + 5V, ATX power is automatically turned off. .<br> <br> 7. protection circuit <br> <br> In order to guarantee safety, ATX power supply set various protection circuits, switching power supply over voltage, over current protection circuit fails to start, switch the power to stop working .to protect the load and the power supply itself. <br> <br> 8. output circuit: <br> <br> Enter the rectifier filtering circuit AC power for rectifier filtering, primary transformation circuits provide ripple smaller DC voltage. Patch in motherboard .cable contains power supply output voltage of the channel and control signals, ATX power output wire all pin definitions see table 1, the output of the current rating shown in table 2. <br> <br> Table 1 power output cable feature list <br .> <br> Pin12345678910 <br> BR> wire color orange orange black red and black red and black grey purple yellow <br> <br> Function 3.3V provides + 3.3V power <br> <br> 3.3V provides + 5V power .supply ground 3.3V provide + 5V power supply + 5V ground wire 5V power supply ground PowerOK power good work + 5VSB power supply + 5VStandby for power starting circuits <br> <br> Provide + 12V power supply 12V <br> <br> Pin11121314151617181920 .<br> <br> Wire color orange blue black green black black black red white red <br> <br> Function 3.3V provides + 3.3V power-12V-12V power supply <br> <br> Ground power start signal, PS .-ON low level-power on, power off the high-<br> <br> Earth ground ground-5V-5V power supply 5V supply + 5V power supply + 5V power supply 5V <br> <br> Various table 2ATX power supply .voltage, rated output current: (A) <br> <br> The output power supply 5V + of + 12V + 3.3V-5V-12V + 5VSB <br> <br> Rated output current 21A6A14A0.3A0.8A0.8A < .br> <br> 9, PW-OK signal of formation: <br> <br> PW-OK signal (AT power supply and power plate called PG signal) for PC post start signal, in order to prevent the road on power output .circuit timing, CPU or part is not to enter the initialization status result in error and suddenly, the hard disk head is too late to the landing area disc scratching, computer power supply are set PW-OK signal. <br> <br> 10 ., + 3 .3 V secondary voltage circuit: <br> <br> Output in motherboard + 3 .3 V typically CPU and other accessories supply, ATX power supplies in general the automatic control voltage, on the basis of T1 secondary + 3 .3 V output .load network created a second automatic voltage control circuit for + 3 .3 V output more accurate and stable. <br> <br> Longitudinal described, on power up the 220V AC voltage with rectifier filter circuit, output + 300V DC high voltage. This voltage .is also added to the push-pull switching circuit and auxiliary power, as a result of push-pull switching circuit switching power tubes have no incentive pulse and standby. Auxiliary power supply voltage on the job will start work, sent out a pulse width modulation .circuit, PS-ON control circuits, protection circuit voltage and motherboard + 5VSB standby, but it is not getting PS-ON host control signal, PS-ON control circuit output latch PWM pulse width modulation circuit so that it does not, at this time .the power is in the standby state. Press the Panel power on trigger switch, control circuit controlled PS-ON signal, unlock the PWM circuit, PWM circuit begins work, output controlled pulse width variable AC impulse drive push-pull switching circuits of push- .pull power tube, and always according to the output voltage ripple to adjust the pulse width, to guarantee the stability of the output voltage. Push-pull switching circuits, push-pull power tubes turn switch, the resulting ripple alternating voltage is switched to the .Deputy-level transformer induction, the output circuit rectifier filtering, host the voltage required. Protection circuit is monitoring the output voltage, over-voltage, under-voltage fails to start in a timely manner so that the PWM circuit stop working in order to ensure .the safety of the circuit and the host. <br> <br> Precision voltage reference ICTL431 <br> <br> Precision voltage reference ICTL431 is T0-92 package as shown in Figure 1. Its performance is output pressure adjustable up to 36V, .operating current range up to 0.1. 100mA, dynamic resistance typical of 0.22 Europe, output clutter. Figure 2 is the typical application of TL431, ② ③, foot ends output voltage V = 2.5 (R2 10 R3) V/R3. If you change .the size of resistance R2, you can change the size of the output voltage. <br> <br> ATX power supply structure characteristics <br> <br> ATX power supply in recent years in the computer in the widely used type of power supply ., it combined with ATX motherboard, but you can manually switch power supply, switching power supply support software for remote control functions. <br> <br> ATX power supply is AT power developed on the basis of, its main circuit also uses the semi .-bridge system switching power supply, but from the architecturally ATX power made the following improvements: <br> <br> 1.ATX power added a secondary switching power supply, as shown in the figure. When AC input ATX power supply in case of .AC 220V, auxiliary power began to work, all the way through rectifier 7805 three-Terminal regulators voltage, output + 5V supply ATX motherboard internal part in shutdown state to keep the work of the chip, such as network communication interface power supply monitoring unit as .part of the system clock chip to use; the other one through rectifier filtering, output secondary + 12V power supply ATX power supply internal TL494, chip work for ATX power main transform circuit starts. <br> <br> 2. integrated power supply connector .interface. ATX power supply with a 20 foot square double-row integrated plug-ins to provide power to the motherboard. <br> <br> 3. output voltage is different. ATX power supply increased 3.3V + 5V power supply and a PS .-ON control input ports, of which 3 .3 V mainly CPUPCI bus-powered. <br> <br> 4. the power of start in different ways, ATX power supplies are generally not set AC switch, with TL494 pulse width control chip and .LM339 comparison of its control of the amplifier. Its characteristics are reference TL494 4 feet of dead zone control function, when the auxiliary power, all the way to output + 5V to the motherboard, the other one output + 12V power supply TL494, passing through .the chip voltage circuit, by 14 feet output + 5V, andAnd 1315 feet touch, then by a divider circuits to LM339 voltage comparator of the reverse side, the back-end voltage about 4.5V. when PS-ON to + 5V, LM339 output .as high level 5V, 811 feet no TL494 output pulse, primary transformation circuits, power is in hibernation. When PS-ON to 0V output to 0V, TL494 of 811 feet output pulse, primary transformation circuits start work. Therefore, we not only can .manually by pressing the trigger button on the host switch to start for low-level PS-ON power, you can also use the program or other means, such as the keyboard PS-ON initiate power for low level, allowing the ATX power supply has .the function of the remote control. <br> <br> <br> <br> <br>.